Method of making an encapsulated filtered feedthrough for an implantable medical device

ABSTRACT

An encapsulated filtered feedthrough assembly for an implantable medical device including a ferrule, an electrical insulator coupled to the ferrule, a printed circuit board (PCB), a feedthrough conductor extending through the electrical insulator and the PCB, and a capacitor coupled to the PCB. The encapsulated filtered feedthrough assembly can include a mold defining an opening and located with respect to the printed circuit board such that at least a portion of the capacitor is positioned within the opening. A first non-conductive material can underfill the capacitor and a second non-conductive material can be backfilled into the mold to encapsulate the capacitor.

CLAIM OF PRIORITY

This application is a divisional of U.S. application Ser. No.15/080,122, filed Mar. 24, 2016, now U.S. Pat. No. 9,937,354, whichclaims the benefit of priority under 35 U.S.C. § 119(e) of U.S.Provisional Patent Application Ser. No. 62/140,606, filed on Mar. 31,2015, which is herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to medical devices and, inparticular, to encapsulated filtered feedthrough assemblies forimplantable medical devices.

BACKGROUND

Implantable medical devices (IMDs) are implantable or partiallyimplantable. Some examples of IMDs include cardiac function management(CFM) devices such as implantable pacemakers, implantable cardioverterdefibrillators (ICDs), cardiac resynchronization therapy devices (CRTs),and devices that include a combination of such capabilities. The devicescan be used to treat patients or subjects using electrical or othertherapy, or to aid a physician or caregiver in patient diagnosis throughinternal monitoring of a patient's condition. The devices may includeone or more electrodes in communication with one or more senseamplifiers to monitor electrical heart activity within a patient, andoften include one or more sensors to monitor one or more other internalpatient parameters. The devices can be implanted subcutaneously and caninclude electrodes that are able to sense cardiac signals without beingin direct contact with the patient's heart. Other examples of IMDsinclude implantable diagnostic devices, implantable drug deliverysystems, or implantable devices with neural stimulation capability(e.g., vagus nerve stimulator, baroreflex stimulator, carotid sinusstimulator, deep brain stimulator, sacral nerve stimulator, etc.).

IMDs can include circuitry mounted within a hermetically-sealed devicehousing. The circuitry can be operatively connected to a lead which isimplanted on or in the heart. The circuitry can be used for, forexample, generating electrical signals that are delivered to thepatient's heart through one or more feedthrough conductors that passfrom the interior of the device housing to the exterior of the devicehousing. The feedthrough assembly provides a mechanism for electricalsignal transfer through the hermetically sealed device housing. Thishermetic seal serves to isolate the circuitry within the metal case fromtissue, blood, and other patient fluid.

In addition to the electrical signals generated by the circuitry of theIMD, externally generated electromagnetic signals can also pass throughthe hermetic seal via the feedthrough assembly and interfere with properoperation of the implantable medical device. Thus, electromagneticinterference filters can be integrated into IMDs to filter theseexternally generated electromagnetic signals to maintain the intendedvoltage levels along the feedthrough conductors.

SUMMARY

The present disclosure is directed toward encapsulated filteredfeedthrough assemblies, IMDs including the encapsulated filteredfeedthrough assembly, and methods for making the same. The presentinventors have recognized, among other things, that existing filteredfeedthrough assemblies include high voltage capacitors that are denselypackaged in a confined space. However, having high voltage capacitors insuch confined spaces can promote high electrical field intensities,which can lead to the dielectric breakdown of air surrounding the highvoltage components (e.g., capacitors) and can result in arcing, failure,and the loss of therapy delivery to a patient.

The encapsulated filtered feedthrough assemblies of the presentdisclosure can provide protection from the detrimental effects ofconcentrated electrical fields and mitigate high voltage breakdownfailures of air gaps between components. The present inventors haverecognized that encapsulating the capacitors with non-conductivematerials can provide an encapsulated filtered feedthrough assembly thatprovides a high degree of dielectric isolation and can mitigate the highelectric field breakdown issues associated with electric fieldcompression in confined spaces. Further, non-conductive materialsencapsulating the capacitors provide a higher voltage breakdownthreshold than compared to air and the encapsulated filtered feedthroughassemblies can be used to facilitate designs with tighter spacing andtherefore smaller size.

To better illustrate the encapsulated filtered feedthrough assemblies,IMDs including the encapsulated filtered feedthrough assemblies, andmethods disclosed herein, a non-limiting list of examples is providedhere:

Example 1 can include subject matter (such as a device) comprising aferrule configured to be attached to a device container of theimplantable medical device; an electrical insulator coupled to theferrule by a connection element; a printed circuit board; a feedthroughconductor extending through the electrical insulator and the printedcircuit board; a capacitor electrically coupled to the printed circuitboard, wherein a gap is formed between the capacitor and the printedcircuit board; a first non-conductive material disposed at leastpartially within the gap; a mold defining an opening and located withrespect to the second side of the printed circuit board such that atleast a portion of the capacitor is positioned within the opening; and asecond non-conductive material disposed within the mold, the secondnon-conductive material encapsulating at least a portion of thecapacitor.

In Example 2, the subject matter of Example 1 can optionally include aplurality of feedthrough conductors extending through the printedcircuit board; and a plurality of capacitors each associated with one ofthe plurality of feedthrough conductors, wherein the mold includes aplurality of openings such that at least one capacitor is positioned atleast partially within a corresponding opening.

In Example 3, the subject matter of one or both of Examples 1 and 2 canoptionally include where at least two layers of the secondnon-conducting material and a portion of the mold are positioned betweentwo adjacent capacitors.

In Example 4, the subject matter of one or any combination of Examples1-3 optionally includes where a height of the mold extends beyond aheight of the capacitor.

In Example 5, the subject matter of one or any combination of Examples1-4 can optionally include where the first non-conductive material andthe second non-conductive material are a different type of material fromthe mold.

In Example 6, the subject matter of one or any combination of Examples1-5 can optionally include where the first non-conductive material andthe second non-conductive material include a curable epoxy resin and themold includes silicone.

In Example 7, the subject matter of one or any combination of Examples1-6 can optionally include where the printed circuit board is amulti-layer circuit board.

Example 8 can include subject matter (such as a device), or canoptionally be combined with the subject matter of one or any combinationof Examples 1-7 to include such subject matter, comprising a devicecontainer including an electronic module within the device container; aheader including a header core and a header shell disposed around theheader core, wherein at least one electrical contact is positionedwithin the header core; a feedthrough assembly configured toelectrically couple the electronic module within the device container toat least one electrical contact, the feedthrough assembly including: acapacitor electrically coupled to a printed circuit board, wherein a gapis formed between the capacitor and the printed circuit board; a firstnon-conductive material disposed at least partially within the gap; amold defining an opening and located with respect to the printed circuitboard such that at least a portion of the capacitor is positioned withinthe opening; and a second non-conductive material disposed within themold, the second non-conductive material encapsulating at least aportion of the capacitor.

In Example 9, the subject matter of Example 8 can optionally includewhere the feedthrough assembly further includes: a ferrule configured tobe attached to the device container; an electrical insulator coupled tothe ferrule by a first connection element; a plurality of feedthroughconductors extending through the printed circuit board and theelectrical insulator, the plurality of feedthrough conductors coupled tothe electrical insulator by a second connection element; and a pluralityof capacitors each associated with one of the plurality of feedthroughconductors, wherein the mold includes a plurality of openings such thatat least one capacitor is positioned at least partially within acorresponding opening.

In Example 10, the subject matter of one or any combination of Example 8or Example 9 can optionally include where at least two layers of thesecond non-conducting material and a portion of the mold are positionedbetween two adjacent capacitors.

In Example 11, the subject matter of one or any combination of Examples8-10 can optionally include where the first non-conductive material andthe second non-conductive material are a different type of material fromthe mold.

Example 12 the subject matter of one or any combination of Examples 8-11can optionally include where the first non-conductive material and thesecond non-conductive material include a curable epoxy resin and themold includes silicone.

Example 13 can include subject matter (such as a method), or canoptionally be combined with the subject matter of one or any combinationof Examples 1-12 to include such subject matter, comprising coupling acapacitor to a printed circuit board, wherein a gap is formed between afirst surface of the printed circuit board and a second surface of thecapacitor; disposing a feedthrough conductor through the printed circuitboard; introducing a first non-conductive material into the gap to atleast partially underfill the capacitor with the first non-conductivematerial; locating a mold with respect to the printed circuit board, themold including an opening configured to receive at least a portion ofthe capacitor when the mold is in location with respect to the printedcircuit board; and introducing a second non-conductive material into themold to encapsulate at least a portion of the capacitor.

In Example 14, the subject matter of Examples 13 can optionally includecoupling the capacitor to the printed circuit board including coupling aplurality of capacitors to the printed circuit board, and wherein themold includes a plurality of openings, each opening separate from eachother and configured to receive at least a portion of at least onecorresponding capacitor of the plurality of capacitors when the mold isin location with respect to the printed circuit board.

In Example 15, the subject matter of one or any combination of Example13 or Example 14 can optionally include coupling the conductor to atleast one of the printed circuit and an electrical insulator; andcoupling the mold to the printed circuit board using the firstnon-conductive material.

In Example 16, the subject matter of one or any combination of Examples13-15 can optionally include curing the first non-conductive material;and curing the second non-conductive material.

In Example 17, the subject matter of one or any combination of Examples13-16 can optionally include introducing the first non-conductivematerial onto the first surface of the printed circuit board; andallowing the first non-conductive material introduced onto the printedcircuit board to be wicked into the gap.

In Example 18, the subject matter of one or any combination of Examples13-17 can optionally include where the mold is formed of a thirdnon-conductive material.

In Example 19, the subject matter of Example 18 can optionally includewhere the first non-conductive material and the second non-conductivematerial are a different type of material from the third non-conductivematerial.

In Example 20, the subject matter of Example 18 can optionally includewhere the third non-conductive material include silicone and the firstnon-conductive material and the second non-conductive material include acurable epoxy resin.

Example 21 can include, or can optionally be combined with any portionor combination or any portions of any one or more of Examples 1-20 toinclude, subject matter that can include means for performing any one ormore of the functions of Examples 1-20, or a machine-readable mediumincluding instructions that, when performed by a machine, cause themachine to perform any one or more of the functions of Examples 1-20.

These non-limiting examples can be combined in any permutation orcombination.

These and other examples and features will be set forth in part in thefollowing Detail Description. This Summary is intended to provide abrief overview of subject matter of the present patent application. Itis not intended to provide an exclusive or exhaustive explanation of theinvention. The detailed description is included to provide furtherinformation about the present patent application such as a discussion ofthe dependent claims and the interrelation of the dependent andindependent claims in addition to the statements made in this section.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. The drawings illustrate generally, by way of example, butnot by way of limitation, the various examples discussed in the presentdocument.

FIG. 1 illustrates an example of an implantable medical device (IMD).

FIG. 2 illustrates an expanded view of an example of a portion of theencapsulated feedthrough assembly.

FIG. 3 illustrates a bottom view of an example of the portion of theencapsulated feedthrough assembly shown in FIG. 2.

FIG. 4 illustrates a side view of an example of a portion of anencapsulated feedthrough assembly.

FIG. 5 illustrates a cross-sectional view of an example of theencapsulated feedthrough assembly.

FIG. 6 illustrates another cross-sectional view of an example of theencapsulated feedthrough assembly.

FIG. 7 shows a flow diagram of an example method of making anencapsulated filtered feedthrough assembly for an IMD.

FIG. 8A illustrates an example of a printed circuit board (PCB).

FIG. 8B illustrates an example of capacitors coupled to the PCB in FIG.8A.

FIG. 8C illustrates an example of the first non-conductive materialdeposited onto the PCB in FIGS. 8A-8C

FIG. 8D illustrates a mold coupled to the PCB in FIG. 8C.

FIG. 8E illustrates an example of the mold in FIG. 8D backfilled with asecond non-conductive material to encapsulate the capacitors.

While the disclosure is amenable to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and are described in detail below. Theintention, however, is not to limit the disclosure to the particularembodiments described. On the contrary, the disclosure is intended tocover all modifications, equivalents, and alternatives falling withinthe scope of the disclosure as defined by the appended claims.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and specific embodimentsin which the disclosure may be practiced are shown by way ofillustration. It is to be understood that other embodiments may be usedand structural changes may be made without departing from the scope ofthe present disclosure.

The present disclosure is directed toward an encapsulated feedthroughassembly for, for example, IMDs that include a printed circuit board(PCB) with at least one capacitor electrically coupled to the PCB. Theencapsulated feedthrough assembly can include a first non-conductivematerial disposed at least partially within a gap formed between the PCBand the at least one capacitor. The feedthrough assembly can furtherinclude a mold that defines an opening and is located with respect tothe printed circuit board such that at least a portion of the capacitoris positioned within the opening when the mold is coupled to the PCB. Inan example, a second non-conductive material can be disposed within themold to encapsulate at least a portion of the capacitor. The first andsecond non-conductive materials, along with the mold, can encapsulatethe capacitor and provide a high voltage breakdown threshold and can beused to reduce the detrimental effects of concentrated electric fields.

FIG. 1 illustrates an example of an 1 MB 10. The 1 MB 10 can include anelectronics unit, such as a pulse generator 20 and at least one lead 18.The pulse generator 20 can be, for example, implanted into asubcutaneous pocket made in the upper pectoral region of a patient.Alternatively, the pulse generator 20 can be placed in a subcutaneous orsubmuscular pocket made in the abdomen, or in other locations of thepatient.

The pulse generator 20 generally includes a hermetically sealed devicehousing 22 including an electronic module 25 and a header 26. The header26 can include a header core 27 and a header shell 28 disposed aroundthe header core 27. The header 26 can be mechanically and electricallycoupled to the device housing 22. The electronic module 25 can include apower supply such as a battery, a capacitor, and other components housedin the device housing 22. The pulse generator 20 can also includeelectrical circuitry, such as a microprocessor, to provide processing,evaluation, or to determine and deliver electrical shocks or pulses ofdifferent energy levels or timing for defibrillation, cardioversion, orpacing to a heart such as in response to cardiac arrhythmia includingfibrillation, tachycardia, heart failure, and bradycardia.

In some examples, the pulse generator 20 can include an antenna withinthe header 26 configured to wirelessly transfer informationelectromagnetically to an external module. The external module caninclude a physician programmer, a bedside monitor, or other relativelynearby assembly used to transfer programming instructions orconfiguration information to the implantable pulse generator 20, or toreceive diagnostic information, a disease status, information about oneor more physiologic parameters, or the like, from the pulse generator20. The external module can be communicatively connected to one or moreother external assemblies, such as a remote external assembly, locatedelsewhere (e.g., a server, a client terminal such as a web-connectedpersonal computer, a cellular base-station, or anotherwirelessly-coupled or wired remote assembly).

The at least one lead 18 can include a lead body 19 having a proximalend 21, where the lead 18 can be coupled to the header 26 of the pulsegenerator 20. The lead 18 can extend to a distal end 23, which can becoupled with a portion of a heart 16, when implanted. The distal end 23of the lead 18 can include one or more electrodes 12, 13, 14. The one ormore electrodes 12, 13, 14 can be located medially or at other locationsalong the lead 18. At least one electrical conductor can be disposedwithin the lead 18, such as to extend from the proximal end 21 to atleast one respective electrode(s) 12, 13, 14. The electrical conductorscarry electrical current and pulses between the pulse generator 20 andthe electrode(s) 12, 13, 14.

In the example illustrated in FIG. 1, the lead 18 can includedefibrillation electrodes, such as for delivering defibrillation therapyvia a first defibrillation electrode, for example, electrode 12 and/or asecond defibrillation, for example, electrode 13. The lead 18 caninclude additional electrodes, such as for delivering pacing therapy viaa pacing/sensing electrode 14. In various examples, the lead 18 can alsoinclude an additional tip electrode at the distal end thereof, which inconjunction with the pacing/sensing electrode, for example, electrode 14can provide for bi-polar pacing and sensing capabilities. While theexample in FIG. 1 includes one lead and three electrodes configured tobe positioned within the heart, the number and location of the leads andelectrodes can vary depending on the type of therapy to be provided andthe type of IMD.

In the example shown in FIG. 1, the lead 18 is shown extending into theright ventricle of the heart 16. In other examples, additional leads canbe coupled to the pulse generator 20 for implantation within, forexample, the right atrium and/or the coronary venous system (e.g., forpacing/sensing of the left ventricle in a bi-ventricular pacing scheme).

In some examples, the IMD 10 can be suitable for use as or with one ormore implantable electrical stimulators, such as, but not limited to,pulse generators, neuro-stimulators, skeletal stimulators, centralnervous system stimulators, or stimulators for the treatment of pain.The system can also be utilized as a sensor or a receiver. Theelectrodes can be used, for sensing, pacing, and/or shocking, forexample.

An example of an encapsulated feedthrough assembly 30 (also referred toherein as “feedthrough assembly 30”) is schematically shown in FIG. 1.The feedthrough assembly 30 can be attached to a hole in the devicehousing 22 and is attached so that the device housing 22 is hermeticallysealed. The feedthrough assembly 30 can include a plurality offeedthrough conductors 32 mounted within and extending from an interiorof the device housing 22 to an exterior of the device housing 22. Thefeedthrough assembly 30 can further include a ground wire 34 directlyattached to a ferrule (see ferrule 36 in FIG. 2). The ground wire 34, inan example, can be located and attached to electronics on the interiorside of the device housing 22 and is not exposed on the exterior side ofthe device housing 22.

FIG. 2 illustrates an example of an expanded view of a portion of theencapsulated feedthrough assembly 30. The feedthrough assembly 30 caninclude an elongate metallic ferrule 36 (also referred to herein as“ferrule 36”) having a longitudinal axis 31, a first end 38, a secondend 40, and a central portion 43 located between the first end 38 andthe second end 40. The ferrule 36 can be mounted to the device housing22 (shown in FIG. 1) of the IMD 10 by fitting the ferrule 36 into a holein the device housing 22 and laser welding the ferrule 36 at an outerperimeter of the ferrule 36. In some examples, the ferrule 36 can beformed of titanium. In other examples, the ferrule 36 can be formed ofother metallic materials.

The feedthrough assembly 30 can include an electrical insulator 42 (alsoreferred to herein as “insulator 42”), which may be mounted within orcoupled to the ferrule 36, for example, using gold brazing techniques.The electrical insulator 42 can include a plurality of holes 44extending through the insulator 42 through which the feedthroughconductors 32 may pass. In some examples, the electrical insulator 42can include, but is not limited to, ceramics, glass, and plastics. Asshown in FIG. 2, the feedthrough assembly 30 can include a plurality offeedthrough conductors 32. The feedthrough conductors 32 can be mountedwithin and extend through a respective feedthrough hole 44 so as toextend from an exterior side 46 to an interior side 48 of thefeedthrough assembly 30.

The feedthrough conductors 32 can be hermetically connected to theelectrical insulator 42 at the holes 44, for example, using agold-brazed joint, soldered joint, welded joint, or other couplingmethods providing a hermetic connection between the feedthroughconductors 32 and the electrical insulator 42. The feedthroughconductors 32 can operate to electrically couple the electrodes 12, 13,14 (shown in FIG. 1) of lead 18 to the pulse generator circuitry withinthe inner region defined by the device housing 22 of the pulse generator20. In various examples, the feedthrough conductors 32 can be pins,wires (e.g., palladium and its alloys, platinum and its alloys,titanium, molybdenum, or gold-plated wires), or a combination thereof.

In some examples, the ground wire 34 can be directly attached to thecentral portion 43 of the ferrule 36. In other examples, the ground wire34 can be electrically coupled to the ferrule 36 by welding or brazing.In some examples, the ground wire 34 and/or the ground pin can comprisea circuit trace, weld, brazing joint, via, electrically conductive epoxyresin, or any other conductive material configured to provide anelectrical ground to the feedthrough assembly 30. In certain examples,the ground wire 34 and/or ground pin can be centrally located alongfeedthrough assembly 30 with respect to the plurality of feedthroughwires 32. In an example, the ground wire 32 does not pass through oralongside the insulator 42. The ground wire 32 can be located on theinterior side 48 and is not exposed on the exterior side 46 and thusdoes not require hermetic connection. Furthermore, though a singleground wire 34 is shown, a plurality of ground wires 34 and/or groundpins can be provided in the feedthrough assembly 30 to provide parallelground paths for electromagnetic signals to be filtered. In variousexamples, the ground wire 34 and/or ground pin can be omitted.

As illustrated in FIG. 2, the feedthrough assembly 30 can include aprinted circuit board (PCB) 50 and a plurality of capacitors 52. The PCB50 can include a plurality of holes 54 extending therethrough. Whenassembled, the feedthrough conductors 32 can be positioned through theholes 54 of the PCB 50. The PCB 50 can provide the electrical couplingbetween the capacitors 52 and the feedthrough conductors 32 viaelectrical traces on the PCB 50 that are electrically coupled to aconductor terminal on each capacitor 52.

In some examples, the PCB 50 can be a multi-layer PCB including aplurality of ground layers separated by suitable insulating layers. Forexample, the multi-layer PCB can have three ground layers and threeinsulating layers, though any number of ground layers or insulatinglayers are contemplated by the present disclosure. Additionally, in someexamples utilizing one or more ground pins, the PCB 50 can include thesame number of ground pins as the number of ground layers in themulti-layer PCB.

In an example, the PCB 50 can include a multilayer FR4 PCB. Insulatinglayers can include any electrical insulating material or dielectric,such as, but not limited to, FR4, epoxy glass, polyimide, silicates, orthe like. Additionally, the ground layers of the multilayer PCB caninclude layers of conductive material, which may include any conductivematerial, such as, but not limited to copper, or any other conductivemetal or semiconductor. In some examples, one or more layers of aluminumfoil may be laminated to one or both sides of an insulating material(e.g., FR4 material) to form alternating ground and insulating layers.

In some examples, the capacitors 52 can have a breakdown voltage that isconfigured to withstand defibrillation or electrocautery voltages thatmay be introduced to the feedthrough assembly 30. For example, thecapacitors 52 can have a breakdown voltage in the range of 400 volts to2000 volts, such as a breakdown voltage of about 1000 volts.Furthermore, capacitors 52 can be ceramic capacitors and be configuredto be surface-mounted to the PCB 50 and/or wire-mounted or solderedthereto. Additionally, the capacitors 52 can have a capacitance valueconfigured to filter signals having a particular frequency. For example,in some examples, capacitors 52 can have capacitance values configuredto attenuate signals having frequencies in a band utilized, for example,in mobile telephones or magnetic resonance imaging processes.

As discussed herein, a gap can be formed between the capacitors 52 andthe PCB 50 when the capacitors 52 are coupled to the PCB 50. A firstnon-conductive material can be disposed within the gap. Underfilling thecapacitors 52 with the first non-conductive material can minimize theair surrounding the capacitor and provide higher voltage breakdownthreshold between adjacent components.

The feedthrough assembly 30 can include a mold 59. The mold 59 candefine openings extending through the mold 59. For example, the mold 59illustrated in FIG. 2 can include a plurality of openings 56 that arepositioned along the sides of the mold 59 and extend from the top side55 of the mold 59 to the bottom side 57 of the mold 59. When assembled,the openings 56 can be configured to receive at least a portion of atleast one corresponding capacitor 52. In some examples, each openingalong the side of the mold 59 can receive a single capacitor 52. Forexample, opening 56A can receive single capacitor 52A. In some examples,an opening 56 can be configured to receive more than one capacitor 52.For example, opening 56B can be configured to receive two capacitors 52.In an example where more than one capacitor 52 is positioned within asingle opening 56, the capacitors 52 can be coupled to the PCB 50 suchthat there is no voltage potential difference between the capacitors 52,for example, when the same terminal (e.g., negative or positive) of thetwo capacitors 52 are adjacent to each other.

In an example, the mold 59 can also include an opening 58 that is anelongated opening positioned along the center of the mold 59. Whenassembled, the central opening 58 can be configured to receive thefeedthrough conductors 34 that extend through the PCB 50. The opening 58can be one single opening that can receive all of the feedthroughconductors or mold 59 can include a plurality of openings along thecenter of the mold 59 such that each opening in the center can receiveone or more of the feedthrough conductors 34. Further, while openings 56can be configured to receive one or more capacitors 52 and opening 58can be configured to receive the feedthrough conductors 34, the mold 59can be formed with openings configured to receive one or more of bothcapacitors 52 and feedthrough conductors 34.

As shown in FIG. 2, each opening 56, 58 can be distinct (e.g., separate)from the other openings 56, 58. By providing distinct openings 56, 58,the capacitors 52 can be fenced in and isolated from one another by atleast one layer of the mold 59. While the example shown in FIG. 2includes nine openings 56 located along the sides or perimeter of themold 59 and one central opening 58, the number, location, and shape ofthe openings 56, 58 can vary based on the configuration of thecapacitors 52, the feedthrough conductors 32, and ground wire 34.

The mold 59 can be formed of non-conductive materials. For example, themold 59 can include, but is not limited to, silicone, epoxy resins,thermoplastics, thermoset plastics, and combinations thereof. In someexamples, the mold 59 can be formed of a material that is flexible, suchas, silicone. The flexibility of the mold 59 can assist in forming atight seal between the PCB 50 and the mold 59.

As disused herein, the mold 59 can be coupled to the PCB 50. Once thecapacitors 52 are coupled (e.g., soldered) to the PCB 50, the firstnon-conductive material can be used to underfill the capacitors 52. Thatis, the gap formed between the PCB 50 and the capacitors 52 can befilled with the first non-conductive material. As well as underfillingthe capacitors 52, the first non-conductive material can also be used tocouple the mold 59 to the PCB 50. As discussed herein, the mold 59 canact like a fence and each capacitor 52 can be positioned within acorresponding opening 56 and be surrounded by the mold 59. Once the mold59 is coupled to the PCB 50, a second non-conductive material can bebackfilled into the openings 56, 58 of the mold 59 to encapsulate thecapacitors 52 and surround a portion of the feedthrough conductors 32and ground pin 34. The underfilled and encapsulated capacitors 52, alongwith the mold 59, provide an encapsulated filtered feedthrough assemblywith a high degree of dielectric isolation and can mitigate the highelectric field breakdown issues associated with the electric fieldcompression in confined spaces. While the mold 59 can provide shieldingbetween capacitors 52, the first non-conductive material and the secondnon-conductive material used to underfill and encapsulate the capacitors52 can act to further mitigate high voltage fields that may be presentsurrounding the capacitors 52. Thus, underfilling and encapsulating thecapacitors 52 can minimize air gaps around the capacitors and increasethe dielectric isolation.

FIG. 3 illustrates an example of a bottom view of the portion of theencapsulated feedthrough assembly 30 shown in FIG. 2. As illustrated inFIG. 3, the assembled portion of the encapsulated feedthrough assembly30 includes the PCB 50 and the ferrule 36. The plurality of capacitors52 can be coupled to the PCB 50 and underfilled with the firstnon-conductive material. The mold 59 can be coupled to the PCB 50 by,for example, the first non-conductive material used to underfill theplurality of capacitors 52. As shown in FIG. 3, the mold 59 can includeopenings 56, 58. One or more openings 56 can receive at least a portionof a single corresponding capacitor 52. For example, opening 56A canreceive at least a portion of capacitor 52A and opening 56B can receiveat least a portions of two capacitors 52.

As shown in FIG. 3, the opening 58 of the mold 59 can be an elongatedcentral opening that can surround or fence in the area including thefeedthrough conductors 32 and ground wire 34 extending through the PCB50. While the opening 58 in FIG. 3 illustrates a single opening toreceive all of the feedthrough conductors 32 and ground wire 34, otherconfigurations are possible. For example, more than one central opening58 can be formed in the mold 59 and can be configured to receive one ormore feedthrough conductors 32 and/or ground wire 34.

In some examples, the mold 59 can be formed to include openings thatreceive one or more capacitors 52, one or more feedthrough conductors32, and one or more of both capacitors 52 and feedthrough conductors 32.For example, the openings 56 of the mold 59 can be configured to receivea single capacitor 52, more than one capacitor 52, and one or morecapacitors 52 and one or more feedthrough conductors 32.

As illustrated in FIG. 3, a space 60 can be defined between thecapacitors 52 and the portion of the mold 59 defining the correspondingopening 56. The space 60 can receive the second non-conductive materialto encapsulate the capacitors 52. Additionally, walls 62 of the mold 59positioned between the openings 56 are also positioned between adjacentcapacitors 52, which can shield one capacitor 52 from another.

FIG. 4 illustrates a side view of an example of an encapsulatedfeedthrough assembly 30. As shown, the feedthrough assembly 30 caninclude the ferrule 36 coupled to an insulator 42. The PCB 50 can becoupled to the ferrule 36 and the mold 59. The feedthrough conductors 32can extend through the PCB 50 and the mold 59, where the ground wire 34does not extend through the insulator 42.

FIG. 5 illustrates a cross-sectional view of an example of theencapsulated feedthrough assembly 30. The cross-sectional view in FIG. 5is taken along a portion of the length of the feedthrough assemblyparallel to the longitudinal axis of the feedthrough assembly includingtwo adjacent capacitors 52. FIG. 5 differs from FIGS. 2-4, in that theexample illustrated in FIG. 5 shows the first non-conductive material 68that underfills the capacitors 52 and the second non-conductive material72 that encapsulates the capacitors 52.

As discussed herein, the gap 70 can be formed between the capacitor 52and the PCB 50. As shown in FIG. 5 and discussed herein, the gap 70between the capacitor 52 and the PCB 50 has been filled with the firstnon-conductive material 68.

The PCB 50 can include a layer of soldermask 51 and component attachmentsurface pads 53 (e.g., copper pads). As discussed herein, a portion ofthe soldermask 51 can be removed along a surface of the PCB 50 toincrease the gap 70 formed between the PCB 50 and the capacitor 52.Along with increasing the size of the gap 70, removing a portion of thesoldermask 51 can also expose the component attachment surface pads 53that are electrically coupled to the capacitors 54. For example, eachcapacitor 52 can include a positive terminal and a negative terminalsuch that when the capacitor is coupled to the PCB 50, one terminal iselectrically coupled to one component attachment surface pad 53 and theother terminal is electrically coupled to the other contact pad 53.

The first non-conductive material 68 can be disposed at least partiallywithin the gap 70 to underfill the capacitors 52 and fill the gap 70.“At least partially” as used herein, is defined as providing asufficient amount of the first non-conductive material 68 such that theamount of continuous free air paths between metal features of differentelectrical potential is minimized. In other words, voids within thefirst non-conductive material 68 that expose metal to metal areminimized.

The capacitors 52 can be coupled to the PCB 50 via attachment element76. In some examples, the attachment element 76 can be formed in asoldering operation using a conductive metal such as tin-lead ortin-lead-silver solder.

The first non-conductive material 68 can be used to couple the mold 59to the PCB 50. For example, the first non-conductive material 68 can bedisposed with the gap 70 as well as along a surface of the PCB 50 thatis configured to be coupled to the mold 59. While the mold 59 is shownbeing coupled to a portion of the PCB 50 including the soldermask 51,the mold can be coupled to a location of the PCB that has the soldermaskremoved. The first non-conductive material can include, but is notlimited to, epoxy resins, silicones, and cyanoacrylates. In someexamples, the first non-conductive material can be a one part, heatcurable, fast curing epoxy resin.

As shown in FIG. 5, the openings 56 defined by the mold 59 can eachreceive a corresponding single capacitor 52. In some examples, a singleopening 56 can include one or more capacitors 52. As discussed herein,the openings 56 defined by the mold 59 can be backfilled with the secondnon-conductive material 72 to at least partially encapsulate thecapacitors 52. As discussed herein with respect to the firstnon-conductive material, the second non-conductive material 72 isapplied such that any continuous free air paths between metal featuresof different electric potentials are minimized, such as any voidsexposing metal to metal.

In some examples, at least two layers of the second non-conductivematerial 72 and a portion of the mold 59 can be positioned between twoadjacent capacitors 52. The second non-conductive material can include,but is not limited to, various epoxy resins, silicones, and moldingcompounds. In some examples, the second non-conductive material 72 canbe a UV curable epoxy resin.

As shown in FIG. 5, the capacitors 52 can be underfilled andencapsulated by the first non-conductive material 68 and the secondnon-conductive material 72, where the openings 56 of the mold 59 can bepositioned around the underfilled and encapsulated capacitors 52. Theencapsulated feedthrough assembly 30 can completely encapsulate thecapacitors 52 with the first and second non-conductive material (e.g.,non-conductive epoxy resin) and can isolate the capacitors 52 from eachother by use of mold 59 (e.g., non-conductive material such assilicone).

As discussed herein, the mold 59 can include a third non-conductivematerial. In an example, the first non-conductive material and thesecond non-conductive material can be a different type of material fromthe third non-conductive material. For example, the third non-conductivematerial can be silicone and the first non-conductive material and thesecond non-conductive material can be an epoxy resin.

The first, second, and third non-conductive materials can be selectedfor their electrical properties, which will be dependent on the voltagerequirement for the particular application. For example, the first,second, and third non-conductive materials can have a resistivity,dielectric constant, and dielectric breakdown potential that is greaterthan air. In one example, the encapsulated feedthrough assembly can beused in high voltage applications, for example, including applicationsthat have electrical potentials greater than 1000 Volts Direct Current.In that instance, the resistivity of one or more of the first, second,and third non-conductive materials, can have a resistance value greaterthan 100 Meghoms for each feedthrough conductor to any other feedthroughconductor. In an example, the dielectric constant of one or more of thefirst, second, and third non-conductive materials can be about 3, whichis three times greater than air and the dielectric breakdown potentialof one or more of the first, second, and third non-conductive materialscan be greater than 500 volts/millimeter, whereas air is typically ratedas about 75 volts/millimeter.

Further, while the first, second, and third non-conductive materialshave a resistivity, dielectric property, and dielectric breakdownperformance greater than air, other properties of the materials can beconsidered for their selection. For example, the first non-conductivematerial can have a low viscosity that facilitates free flow under thecapacitor due to capillary flow and minimizes air gaps. The capillaryeffect ensures sufficient fill under the capacitor. In an example, thesecond non-conductive material can have a low viscosity and be UVcurable, which can make the processing of the material fast, easy, andminimize air gaps. Further, the third non-conductive material can bemade out of a flexible material, which can help with gasketing of themold to the PCB.

The feedthrough assembly 30 of the present disclosure, including thefirst, second, and third non-conductive materials, can provide a highdegree of dielectric isolation and can mitigate the high electric fieldbreakdown issues associated with electric field compression in confinedspaces.

FIG. 6 illustrates another cross-sectional view of an example of theencapsulated feedthrough assembly 30. The cross-sectional view in FIG. 6is taken along a width of the feedthrough assembly perpendicular to alongitudinal axis of the feedthrough assembly 30. Similarly to FIG. 5,FIG. 6 differs from FIGS. 2-4, in that the example illustrated in FIG. 6shows the first non-conductive material 68 that underfills thecapacitors 52 and the second non-conductive material 72 thatencapsulates the capacitors 52.

The insulator 42 can be attached to an inner surface of the ferrule 36by an attachment element 74. In various examples, the attachment element74 can be made of an electrically conductive material. In some examples,the attachment element 74 can be formed by a brazing operation using aconductive metal such as gold, alloys of gold, or others which form ahermetic bond between the insulator 42 and the inner surface of theferrule 36. Similarly, the feedthrough conductor 32 can be attached toan inner surface of the insulator 42 and to the PCB 50. The feedthroughconductor 32 can be coupled to the insulator 42 via a brazing operationusing the attachment element 74. The PCB 50 can be coupled to thefeedthrough conductor 32 using attachment element 75. In some examples,the attachment element 75 can be formed in a soldering operation using aconductive metal such as tin-lead or tin-lead-silver solder.

As shown in FIG. 6, the feedthrough conductor 32 extends through a holein the PCB 50. The hole (e.g., hole 54 shown in FIG. 2) extends from atop surface 64 of the PCB 50 to a bottom surface 66 of the PCB 50.

As discussed herein, a gap 70 can be formed between the capacitor 52 andthe PCB 50. As shown in FIG. 6, the gap 70 between the capacitor 52 andthe PCB 50 has been filled with the first non-conductive material 68. Insome examples, the PCB 50 can include a layer of soldermask 51 that hasbeen removed along portions of the PCB 50. The soldermask 51 can beremoved in certain areas to increase the gap 70. The firstnon-conductive material 68 can be disposed at least partially within thegap 70. The first non-conductive material 68 can also be deposited ontoa surface of the PCB 50 to be used to couple the mold 59 to the PCB 50.While the mold 59 is shown being coupled to a portion of the PCB 50including the soldermask 51, the mold 59 can be coupled to a location ofthe PCB 50 that has the soldermask 51 removed. As shown in FIG. 6, theopenings 56 defined by the mold 59 each receive a corresponding singlecapacitor 52. Additionally, the opening 58 defined by the mold 59 canreceive a portion of the feedthrough conductor 32.

As discussed herein, once the mold 59 is coupled to the PCB 50, theopenings 56, 58 of the mold 59 can be backfilled with the secondnon-conductive material 72 to at least partially encapsulate thecapacitors 52 and the feedthrough conductor 32. As shown in FIG. 6, thecapacitors 52 can be underfilled and encapsulated by the firstnon-conductive material 68 and the second non-conductive material 72,where the openings 56 of the mold 59 can be positioned around theunderfilled and encapsulated capacitors 52.

FIG. 7 is a flow diagram of an example method 200 of making anencapsulated filtered feedthrough assembly for an implantable medicaldevice. At step 202, the method 200 can include coupling a capacitor toa printed circuit board, where a gap is formed between a first surfaceof the printed circuit board and a second surface of the capacitor. Forexample, the capacitor 52 can be coupled to the PCB 50, where the gap 70is formed between the PCB 50 and the capacitor 52, as shown in FIGS. 5and 6.

At step 204, the method 200 can include disposing a feedthroughconductor through the PCB. For example, feedthrough conductor 32 can bedisposed through the PCB 50 and the insulator 42, where the feedthroughconductor 32 can be coupled to the insulator 42 and the PCB 50, as shownin FIG. 6.

At step 206, the method 200 can include introducing a firstnon-conductive material into the gap to at least partially underfill thecapacitor with the first non-conductive material. For example, themethod 200 can include introducing the first non-conductive material 68to underfill the capacitor 52, as shown in FIGS. 5 and 6.

At step 208, the method 200 can include locating a mold with respect tothe PCB, the mold including an opening configured to receive at least aportion of the capacitor when the mold is in location with respect tothe PCB. For example, the mold 59 can be located with respect to the PCB50, where the mold 59 includes an opening 56 to receive at least aportion of the capacitor 52 when the mold 59 is in location with respectto the PCB 50. The method 200 can further include coupling the mold 59to the PCB 50 by using the first non-conductive material 68. The method200 can further include curing the first non-conductive material. Forexample, the mold 59 can be placed onto the PCB 50 and in contact withthe first non-conductive material 68 and then subsequently cured tocouple the mold to the PCB.

At step 210, the method 200 can include introducing or backfilling asecond non-conductive material into the mold to encapsulate at least aportion of the capacitor. For example, the second non-conductivematerial 72 can be introduced into the mold 59 to encapsulate at least aportion of the capacitor 52, as shown in FIGS. 5 and 6. The mold 59 canbe formed of a third non-conductive material, such as silicone. Themethod 200 can further include curing the second non-conductivematerial. In some examples, the second non-conductive material can becurable via UV light. In some examples, the mold 59 can be UVtransparent to assist in the curing of the second non-conductivematerial.

FIGS. 8A-8E illustrates underfilling and encapsulating capacitorscoupled to a PCB. FIG. 8A illustrates an example of a PCB 82. As shownin FIG. 8A, the PCB 82 can have a portion of a solder mask 83 removedalong areas 84 of the PCB 82 and have component attachment surface pads85. As discussed herein, a portion of the soldermask 83 can be removedto create a larger gap between a capacitor and the PCB, which is moresuitable for underfilling the capacitors. Along with increasing the sizeof the gap, removing a portion of the soldermask 83 can also expose thecomponent attachment surface pads 85.

FIG. 8B illustrates an example of capacitors 88 coupled to the PCB 82 inFIG. 8A. The capacitors 88 can be coupled to the PCB 82 and can includea top surface 92, a bottom surface 96, and side surfaces 94. Thecapacitors 88 can be coupled to the PCB 82 with an attachment element 98(e. g., solder) such that the attachment element 98 can be positionedalong a portion of the bottom surface 96 and along a portion of the sidesurfaces 94 of the capacitors 88. The component attachment surface pads85 can be electrically coupled to the capacitors 88. For example, eachcapacitor 88 can include a positive terminal and a negative terminalsuch that when the capacitor is coupled to the PCB 82, one terminal iselectrically coupled to one component attachment surface pad 85 and theother terminal is electrically coupled to the other contact pad 85.

Gap 90 can be formed between the bottom surface 96 of the capacitor andthe PCB 82. The gap 90 can be formed having a sufficient distancebetween the PCB 82 and the bottom surface 96 of the capacitor 88 toreceive the underfill (e.g., the first non-conductive material). Forexample, the gap 90 can have a distance between the PCB 82 and thebottom surface 96 of the capacitor 88 that is within a range of about 1thousandth of an inch (mil) to about 5 mils. In some examples, the gap90 can be within a range of about 1 mil to about 3 mils.

FIG. 8C illustrates an example of the first non-conductive material 100deposited onto the PCB 82. The first non-conductive material 100 can bedeposited onto the PCB 82 such that a portion of the firstnon-conductive material 100 flows (e.g., wicks) into the gap 90 tounderfill the capacitors 88. As discussed herein, due to the confinedspace between the capacitors 88 and the PCB 82, the viscosity andtemperature of the first non-conductive material 100 should besufficient to enable the first non-conductive material 100 to be wickedinto the gap 90.

In some examples, the first non-conductive material can be a curableepoxy resin. In that instance, prior to curing the first non-conductivematerial 100, the mold 102 can be located with respect to the PCB 82.The mold 102 can be located with respect to the PCB 82 such thatopenings 103 of the mold 102 receive a corresponding capacitor 88 orcapacitors 88. Once the mold 102 is located with respect to the PCB 82,the first non-conductive material 100 can be cured to couple the mold102 to the PCB 82. In some examples, the first non-conductive materialcan be deposited under the capacitors 88 and another non-conductivematerial can be used to couple the mold 102 to the PCB 82. In thatinstance, the first non-conductive material can be cured prior todepositing the other non-conductive material or the first non-conductivematerial can be cured concurrently with the other non-conductivematerial.

FIG. 8D illustrates an example of the mold 102 having been located withrespect to the PCB 102 such that a capacitor 88 is positioned within acorresponding opening 103 of the mold 102. FIG. 8E illustrates anexample of the mold 102 having been backfilled with a secondnon-conductive material 106 to encapsulate the capacitors 88. Forexample, once the mold 102 is coupled to the PCB 82, the openings 103 ofthe mold 102 can be backfilled with the second non-conductive material106 to encapsulate the capacitors 88. As shown in FIG. 8D, the height108 of the mold 102 extends beyond the top surface 92 of the capacitors88 to ensure that when the mold 102 is backfilled, the capacitor 88 willbe completely encapsulated. That is, the bottom surface 96, the topsurface 92, and the side surfaces 94 are encapsulated by the first andthe second non-conducting materials 100, 106. The underfilled andencapsulated capacitors 88, along with the mold 102 can provide anencapsulated filtered feedthrough assembly with a high degree ofdielectric isolation and can mitigate the high electric field breakdownissues associated with the electric field compression in confinedspaces. While the mold 102 can provide shielding between capacitors 88,the first non-conductive material 100 and the second non-conductivematerial 106 used to underfill and encapsulate the capacitors act tofurther mitigate high voltage fields that may be present surrounding thecapacitor. Thus, underfilling and encapsulating the capacitors 88 canminimize air gaps around the capacitors and increase the dielectricisolation.

ADDITIONAL NOTES

The above detailed description includes references to the accompanyingdrawings, which form a part of the detailed description. The drawingsshow, by way of illustration, specific embodiments in which theinvention can be practiced. These embodiments are also referred toherein as “examples.” All publications, patents, and patent documentsreferred to in this document are incorporated by reference herein intheir entirety, as though individually incorporated by reference. In theevent of inconsistent usages between this document and those documentsso incorporated by reference, the usage in the incorporated reference(s)should be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more.” In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A or B” includes “A but not B,” “B but not A,” and “A and B,” unlessotherwise indicated. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Also, in the following claims, theterms “including” and “comprising” are open-ended, that is, a system,device, article, or process that includes elements in addition to thoselisted after such a term in a claim are still deemed to fall within thescope of that claim. Moreover, in the following claims, the terms“first,” “second,” and “third,” etc. are used merely as labels, and arenot intended to impose numerical requirements on their objects.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) may be used in combination with each other. Otherembodiments can be used, such as by one of ordinary skill in the artupon reviewing the above description. The Abstract is provided to complywith 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain thenature of the technical disclosure. It is submitted with theunderstanding that it will not be used to interpret or limit the scopeor meaning of the claims. Also, in the above Detailed Description,various features may be grouped together to streamline the disclosure.This should not be interpreted as intending that an unclaimed disclosedfeature is essential to any claim. Rather, inventive subject matter maylie in less than all features of a particular disclosed embodiment.Thus, the following claims are hereby incorporated into the DetailedDescription, with each claim standing on its own as a separateembodiment. The scope of the invention should be determined withreference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

What is claimed is:
 1. A method of making an encapsulated filteredfeedthrough assembly for an implantable medical device, the methodcomprising: coupling a capacitor to a printed circuit board, wherein agap is formed between a first surface of the printed circuit board and asecond surface of the capacitor; disposing a feedthrough conductorthrough the printed circuit board; introducing a first non-conductivematerial into the gap to at least partially underfill the capacitor withthe first non-conductive material; locating a mold with respect to theprinted circuit board, the mold including an opening configured toreceive at least a portion of the capacitor when the mold is in locationwith respect to the printed circuit board; and introducing a secondnon-conductive material into the mold to encapsulate the at least aportion of the capacitor.
 2. The method of claim 1, wherein coupling thecapacitor to the printed circuit board includes coupling a plurality ofcapacitors to the printed circuit board, and wherein the mold includes aplurality of openings, each opening separated from each other andconfigured to receive at least a portion of at least one correspondingcapacitor of the plurality of capacitors when the mold is in locationwith respect to the printed circuit board.
 3. The method of claim 1,wherein introducing the first non-conductive material into the gapincludes: introducing the first non-conductive material onto the firstsurface of the printed circuit board; and allowing the firstnon-conductive material introduced onto the printed circuit board to bewicked into the gap.
 4. The method of claim 1, further including:coupling the feedthrough conductor to the printed circuit; and couplingthe mold to the printed circuit board using the first non-conductivematerial.
 5. The method of claim 1, wherein the mold is formed of athird non-conductive material.
 6. The method of claim 5, wherein thefirst non-conductive material and the second non-conductive material area different type of material from the third non-conductive material. 7.The method of claim 5, wherein the third non-conductive materialincludes silicone and the first non-conductive material and the secondnon-conductive material include a curable epoxy resin.
 8. The method ofclaim 1, further including: curing the first non-conductive material;and curing the second non-conductive material.
 9. The method of claim 1,wherein the first and second non-conductive materials are the same. 10.The method of claim 1, wherein the first non-conductive material isdifferent from the second non-conductive material.